If you need to use the uid instead of msgno use
imap_clearflag_full($stream, implode(',', $flags), '\\DELETED', ST_UID);
(PHP 4, PHP 5, PHP 7, PHP 8)
imap_undelete — Desmarcar el mensaje que está marcado para borrar
$imap_stream, int $msg_number, int $flags = 0): boolElimina la bandera de borrado de un mensaje especificado, que está establecida mediante imap_delete() o imap_mail_move().
Devuelve true en caso de éxito o false en caso de error.
If you need to use the uid instead of msgno use
imap_clearflag_full($stream, implode(',', $flags), '\\DELETED', ST_UID);
The imap_delete function allows the option to use a UID for the message number but the imap_undelete function does not.